From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Pittman Subject: Re: Degraded raid5 returns mdadm: /dev/hdc5 has no superblock - assembly aborted Date: Fri, 08 Jul 2005 19:26:37 +1000 Message-ID: <87oe9dlkc2.fsf@enki.rimspace.net> References: <42CDE44C.9020804@phys.unsw.edu.au> <874qb6m0fr.fsf@enki.rimspace.net> <62b0912f05070801436421ea0e@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 8 Jul 2005, Molle Bestefich wrote: >> On 8 Jul 2005, Melinda Taylor wrote: >>> We have a computer based at the South Pole which has a degraded raid 5 >>> array across 4 disks. One of the 4 HDD's mechanically failed but we have >>> bought the majority of the system back online except for the raid5 >>> array. I am pretty sure that data on the remaining 3 partitions that >>> made up the raid5 array is intact - just confused. The reason I know >>> this is that just before we took the system down, the raid5 array >>> (mounted as /home) was still readable and writable even though >>> /proc/mdstat said: > > On 7/8/05, Daniel Pittman wrote: >> What you want to do is start the array as degraded, using *only* the >> devices that were part of the disk set. Substitute 'missing' for the >> last device if needed but, IIRC, you should be able to say just: >> >> ] mdadm --assemble --force /dev/md2 /dev/hd[abd]5 >> >> Don't forget to fsck the filesystem thoroughly at this point. :) > > At this point, before adding the new disk, I'd suggest making *very* > sure that the event counters match on the three existing disks. > Because if they don't, MD will add the new disk with an event counter > matching the freshest disk in the array. That will cause it to start > synchronizing onto one of the good disks instead of onto the newly > added disk.... Happened to me once, gah. Ack! I didn't know that. If the event counters don't match up, what can you do to correct the problem? Daniel -- The problem with defending the purity of the English language is that English is about as pure as a cribhouse whore. We don't just borrow words; on occasion, English has pursued other languages down alleyways to beat them unconscious and rifle their pockets for new vocabulary. -- James D. Nicoll